This a method and apparatus for producing methanol and, in particular, to a method and apparatus for producing methanol using a synthesis gas.
In present day methanol production, the low pressure methanol synthesis process (50-100 atm.; 200.degree.-300.degree. C.), available since the 1960's, is universally favored over the high pressure process (250-350 atm.; 350.degree.-450.degree. C.). In the low pressure porcess, a feedstock having hydrocarbon content, e.g., natural gas, coal, heavy oils, naptha, propane or butane, is first reformed to produce a gas stream rich in hydrogen. This hydrogen-rich gas stream is then adjusted in composition and the resultant stream containing hydrogen, carbon dioxide and carbon monoxide catalytically synthesized to produce the desired methanol.
Usually, the reformation process results in a synthesis gas whose hydrogen content is greater than that needed for the methanol reaction. This excess hydrogen may be used as fuel in the plant or may be cryogenically separated from the synthesis gas stream and used in other applications. Also, CO.sub.2 may be added to the synthesis gas stream to convert some of the hydrogen to CO. This procedure adjusts the stoichiometric number expressed by equation (a) below to the desired value, ##EQU1## thereby increasing the methanol yield. However, the CO.sub.2 added to the gas stream is generally recovered from the reformer flue which is a costly process.
While the above procedures have thus been successfully utilized for methanol production, other procedures which could result in reduced cost are still being sought.
It is, therefore, an object of the present invention to provide an apparatus and method for methanol production.
It is a further object of the present invention to provide a method and apparatus for methanol production utilizing unique means for adjusting the hydrogen content of the synthesis gas.